Ignore the first two images close to the top. They are earlier plots.
On Sat, Apr 26, 2025, 11:33?AM Part 15 Engineer <
kc8gpd@...> wrote:
How does this look? It's a nanovna and nit a calibrated to nist piece of equipment so it's not going to be dead on even when you go through the calibration procedure for the nanovna.
I think this is the best it's going to get.
A number of things:
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- You¡¯re sweeping 30 MHz wide with only 401 points.? You need to either narrow down your sweep just to the range of interest, use more points, or more likely a combination of both.? I¡¯d typically be using a 10 MHz span and 1601 points (I don¡¯t have a NanoVNA, I don¡¯t know what it¡¯s capabilities are).
- Something is either very wrong with the cavity, or the calibration.? It is showing you have 3.129 of insertion loss in the bandpass; it should be about 0.25 dB for a properly-functioning PD526 resonator.? Likewise, at the notch frequency, it¡¯s showing that you have 4.77 dB of return loss ¨C it should be a lot closer to zero.? If I were to take a WAG, you have 3 dB or more of cable loss that isn¡¯t compensated for, and/or something is wrong with your calibration kit.
- No since in working on the full duplexer harnessed together until the above are first addressed and you know each cavity is properly tuned individually.
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--- Jeff WN3A
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Here is the plot for a single cavity.
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Ok, I'm tuning the pd526 on the nvna. I can't seek to get everything to line up on both reject and pass simultaneously. It seems to be one or the other. I have attached pic of my latest plot. This is the best I got it so far. I did tune cavities individually then hook them together. And I got multiple peaks and valleys on the plot instead on one nice peak on the pass and valley on the reject. Does anyone have a link to the plot for the pd526 and what it should look?like?
Thanks
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I think I finally got the pd526 tuned. It has 1db difference in sensitivity between direct input and going through duplexer and very little tx power loss coming out of duplexer. Probably only a few watts of loss. Tomorrow I will do some field testing to see if it gets put as far as the txrx 28-70-15h duplexer I was using. I'm not seeing any signs of desense yet.
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It will have the opposite effect.? To get more dynamic range you would really need an amplifier or a way to drive in more signal.? The pads are just to match the impedance as the output/input terminals may not be the nominal 50 ohms.? That is just for the notches.? If tuning the pass with a RLB do not use a pad as this will give a false match/very low RL .
On Thursday, April 24, 2025 at 11:28:09 AM EDT, Part 15 Engineer via <kc8gpd=[email protected]> wrote:
Will a pad give the nanovna more of a dynamic range to see? the notch depth? Iirc the dynamic range of a standard nvna is about 60 to 80db. So if I put a 10 or 15db pad that should help with tuning the notches?
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Pads can be helpful on the generate side of a VNA providing a good resistive match to the device under test. Many years ago working at Hughes Aircraft we always terminated our generate cables with a 6dB pad.?
